Railroad cars typically have one or more axles, each with a metallic wheel on either end. The wheels rest on a railroad track consisting of metallic rails attached to wooden or metallic ties spaced at regular intervals. The wheels rotate on the rails as the railroad car travels on the railroad track. When brakes are applied to the wheels, however, the wheels can stop rotating and instead slide on the rails before the railroad car slows down or comes to a complete stop.
Repeated sliding motion of the wheels on the rails can cause excessive wear on portions of the wheel in contact with the rails. Specifically, the wheels can develop one or more flattened portions as a result of the repeated sliding motion. When a wheel with one or more flattened portions rotates on the rails, the flattened portions repeatedly impact the rails with each rotation of the wheel, creating excessive vibrations and noise. The forces induced by the flat wheels can cause significant damage to wheel bearings, springs, and other parts of the railroad car. A severely flattened wheel can even cause the railroad car to derail. It is, therefore, important to detect the presence of flat wheels on a railroad car and initiate preventive maintenance before the flat wheels cause significant damage.
An exemplary method of detecting flat wheels is disclosed in U.S. Pat. No. 5,743,495 to Welles II et al. that issued on Apr. 28, 1998 (“the '495 patent”). Specifically, the '495 patent discloses a system for predicting railway hazards utilizing vibration sensors mounted on each respective rail of a railroad track. The vibration sensors detect the vibration of the railroad track caused by a railway vehicle moving along the railroad track. Each sensor is attached to one rail of the railroad track to detect movement of that rail. The sensing axis of each sensor in the '495 patent is oriented at a small angle of about 1° to 10° relative to a longitudinal axis of the rail. The angle of inclination allows each sensor to detect movement along both a horizontal axis and a vertical axis of each rail. The '495 patent also discloses a central processor adapted to detect a flat wheel on a moving railway vehicle by identifying frequency peaks, occurring at or near an expected frequency, in the signals received from the sensors. The '495 patent estimates the expected frequency by dividing a predetermined expected speed of the railway vehicle by the circumference of that vehicle's wheel.
Although the '495 patent discloses a method of detecting flat wheels, the method disclosed in the '495 patent relies on sensors directly attached to the rails. This requires that new sensors must be attached to the rails every time rails are replaced, making this method of flat wheel detection cumbersome and expensive. Moreover, the sensors of the '495 patent may not be sensitive enough to detect the early onset of flattening. A flat wheel on a railroad car is expected to generate vibrations primarily because of the vertical impact of a flat portion of the wheel on the rail. The sensors of the '495 patent, however, are nearly horizontal, making them less sensitive to smaller vertical impacts on the rails caused by relatively smaller flattened portions on a wheel. As a result, these sensors may not be able to detect an early onset of flattening on the wheels because wheels having relatively smaller flattened portions will produce relatively smaller vertical impacts on the rails. Moreover, because the '495 patent uses only one sensor per rail, the sensor may not detect the presence of more than one flat portion on the wheel.
The flat wheel detector of the present disclosure solves one or more of the problems set forth above and/or other problems in the art.